Recently, in a medical field, an X-ray image detection apparatus provided with a detection panel for converting X rays that have been transmitted through a human body into electrical signals and outputting the electrical signals as images instead of radiation films such as X-ray films has been in widespread use. As the detection panel, there are an indirect-conversion type detection panel and a direct-conversion type detection panel. In the indirect-conversion type detection panel, X rays are converted into visible light by phosphors, and the visible light is converted into electric charges by photoelectric conversion elements. In the direct-conversion type detection panel, the X rays are directly converted into electric charges by a photoconductor layer.
The detection panel is contained in a housing. To a surface of the housing at the side nearer to the X-ray generator is attached a surface plate made of carbon-based material having low X-ray absorptivity such as carbon fiber, so that the X rays are efficiently transmitted through the detection panel. On the surface plate are formed a square-frame shaped index as a first index showing a detection range of the detection panel, and a cross-shaped index as a second index showing a center position of the detection range of the detection panel, as disclosed in Japanese Patent Laid-Open Publication No. 2006-6424, for example. Alignment between the detection range of the detection panel and an irradiation field of the X-ray generator is performed using the first and second indices. Additionally, the first and second indices are used for positioning of a subject (human body), so that the subject to be imaged is included within the detection range.
In a radiographic image detection apparatus disclosed in Japanese Patent Laid-Open Publication No. 2006-6424, the indices are generally directly printed on the surface plate by using pigment. Therefore, due to repeated contact with a radiographer and the subject, the indices unfavorably suffer from deterioration such as abrasion and peeling.